Differential effects of the putative GBF1 inhibitors Golgicide A and AG1478 on enterovirus replication

The genus Enterovirus, belonging to the family Picornaviridae, includes well-known pathogens, such as poliovirus, coxsackievirus, and rhinovirus. Brefeldin A (BFA) impedes replication of several enteroviruses through inhibition of Golgi-specific BFA resistance factor 1 (GBF1), a regulator of secretory pathway integrity and transport. GBF1 mediates the GTP exchange of Arf1, which in activated form recruits coatomer protein complex I (COP-I) to Golgi vesicles, a process important in transport between the endoplasmic reticulum and Golgi vesicles. Recently, the drugs AG1478 and Golgicide A (GCA) were put forward as new inhibitors of GBF1. In this study, we investigated the effects of these putative GBF1 inhibitors on secretory pathway function and enterovirus replication. We show that both drugs induced fragmentation of the Golgi vesicles and caused dissociation of Arf1 and COP-I from Golgi membranes, yet they differed in their effect on GBF1 localization. The effects of AG1478, but not those of GCA, could be countered by overexpression of Arf1, indicating a difference in their molecular mechanism of action. Consistent with this idea, we observed that GCA drastically reduced replication of coxsackievirus B3 (CVB3) and other human enterovirus species, whereas AG1478 had no effect at all on enterovirus replication. Time-of-addition studies and analysis of RNA replication using a subgenomic replicon both showed that GCA suppresses RNA replication of CVB3, which could be countered by overexpression of GBF1. These results indicate that, in contrast to AG1478, GCA inhibits CVB3 RNA replication by targeting GBF1. AG1478 and GCA may be valuable tools to further dissect enterovirus replication.